This invention relates to a compressor, and more particularly, to a reciprocating piston type compressor for an air conditioning apparatus which includes a mechanism for adjusting the capacity of the compressor.
Generally, in air conditioning apparatus, thermal control is accomplished by intermittent operation of the compressor in response to a signal from a thermostat located in the room being cooled. Once the temperature in the room has been lowered to a desired temperature, the refrigerant capacity of the air conditioner generally need not be very large in order to handle supplemental cooling because of further temperature changes in the room, or for keeping the room at the desired temperature. However, prior art air conditioners do not have capacity control mechanisms so that, after the room has cooled down to the desired temperature, the manner for controlling the output of the compressor is by intermittent operation of the compressor. Thus, the relatively large load which is required to drive the compressor is intermittently applied to the driving source.
When a compressor is used in an automobile air conditioner, the compressor is driven by the engine of the automobile through an electromagnetic clutch. Such prior art automotive air conditioners face the same load problems described above once the passenger compartment reaches a desired temperature. Control of the compressor is accomplished by intermittent operation of the compressor through the magnetic clutch which couples the automobile engine to the compressor. Thus, the relatively large load which is required to drive the compressor is intermittently applied to the automobile engine.
Furthermore, since the compressor of an automobile air conditioner is driven by the engine of the automobile, the rotation frequency of the drive mechanism changes from moment to moment, which causes the refrigerant capacity to change in proportion to the rotation frequency of the engine. Since the capacity of the evaporator and condenser of the air conditioner does not change, when the compressor is driven at high rotation, the compressor performs useless work. To avoid useless work by the compressor, prior art automobile compressors are controlled by intermittent operation of the magnetic clutch. Therefore, a large load is intermittently applied to the automobile engine.